A ginkgo tree in December has the most brilliant golden foliage you will ever see, and I consider myself privileged to have a few of them growing in my neighborhood. 

The ginkgo is sometimes referred to as a living fossil since the oldest fossil record of any tree belongs to it, with imprints of the ginkgo’s distinctive fan-shaped foliage found in fossils 270 million years old. The ginkgo is thought to be the botanical link between ferns and conifers. Its leaf has a slight notch on top in the center, making it slightly bi-lobed which is responsible for its botanical name of Ginkgo biloba.

Native to China, this is an exceedingly durable tree, whose oldest living specimen is 3,500 years old. Its pollution and smog resistance and virtual immunity to pests and diseases make it a highly desirable tree for the urban landscape, or at least for public parks. It has been planted as a street tree on the corner of Beverly Glen Boulevard and Moorpark Street in Sherman Oaks, yet this will present a maintenance challenge in years to come since ginkgos may eventually reach a height of 60 feet with a 40-foot spread. 

The toughness of the ginkgo was recognized following the detonation of an atomic bomb on Hiroshima in Japan during World War II. Only six trees, all of them ginkgos, survived the blast, and all of these are still alive today. One of the six had been planted around 1700.

The ginkgo is dioecious, which means that trees are either male or female. The females produce malodorous fruit so that the only ginkgo trees found in the nursery trade are males. Buds from male trees are grafted onto seedlings to ensure that the resulting tree will never bear fruit.

Extract from ginkgo leaves is used for treatment of a variety of ills. While it is true that ginkgo extract has a high concentration of antioxidants and therefore can lay claim to certain anti-inflammatory properties, its power to cure disease has never been conclusively proven. While ginkgo extract by itself has not been shown to improve memory, there is some evidence that it could be beneficial in this area when used in combination with medications that have proved to delay the onset or advance of dementia.

A gardener from the Redlands area wrote to me as follows: “I have two Hachiya persimmon trees growing about 30 feet apart. This year, for the first time, they set no fruit. Now, one tree has yellow leaves while the other is stubbornly holding onto green leaves. In the past 35 years, they both have reliably borne fruit and colored in the fall. Thanks for any explanations you might have.”

My first thought regards microclimate and/or care for your trees this year as opposed to previous years: Are overhanging branches from taller trees perhaps taking away light that is needed for flower and fruit production? Is there excessive leafy growth that demands so much of the trees’ resources that nothing is left over for fruit? Were trees watered or fertilized more than usual this year? Also, if your trees yielded a large crop last year, that would explain lack of fruit this year since persimmons tend to bear in alternate years. 

Finally, if your trees have not been pruned in a while, excessive leafiness could cast shade on the interior of the tree, preventing flower bud development and/or fruit growth.The lack of colorful leaves could be attributable to insufficiently cold fall weather since leaf color change depends on a proper dose of cold. This past September was the hottest in our area in the past 128 years and October saw plenty of 90-degree days. 

A correspondent in Riverside emailed the following question: “My first-year pink trumpet tree (Tabebuia heterophylla) is looking troubled. Any thoughts on how I can help her?” I am assuming that your tree gets at least four hours of direct sunlight in winter but six to eight during the growing season. Otherwise, it could be suffering from insufficient light. I will also assume that soil drainage is good. Assuming that light exposure and soil drainage are not problematic, it might just be a matter of the tree acclimating itself to your garden conditions. Many trees and other woody perennials struggle for a year or two before settling into their surroundings and putting out robust growth. My own butterfly bush (Cassia bicapsularis) has been in the ground for two years but only last month did it flower profusely. This exceptional plant, which is actually a small tree, can be found exclusively, to the best of my knowledge, at Worldwide Exotics (woroldwideexoticsnursery.com) in Sylmar. Many other rare plants from the collection of legendary plant explorer Gary Hammer are still available there. Getting back to your tree, I should also mention that Tabebuias are semi-evergreen which means that they go through a brief period of dormancy around this time of year.

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California native of the week: Southern maidenhair fern (Adiantum capillus-veneris) is an elegant beauty with tiny leaves that compose a fine, soft-textured and welcoming specimen planted in a shady planter by your front door. Maidenhairs are somewhat water-needy, especially when they are establishing during their first two years in the garden, but are rather self-sufficient after that. Many familiar species of ferns are characterized by a sort of scruffiness, but not maidenhairs. Maidenhair ferns have smooth, diminutive, fan-shaped leaflets that invite you to touch them. Their lime green color contrasts nicely with wiry black stems. Adiantum, maidenhair’s genus name, means “water repellent” in Greek and refers to the slippery and somewhat leathery texture of its foliage. The common name of maidenhair fern owes it origin to the silky hairs that grow out of its roots, whose vigor resembles that of the healthy tresses of a young woman. Moreover, a decoction of maidenhair roots was once thought to stimulate hair follicles and combat baldness.

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